This invention relates to a coiled tubing drilling and service unit and method and, more particularly, to such a unit and method for running both wireline and coiled tubing into and from the bore of a high pressure oil and gas well.
A great variety of well servicing operations are routinely performed inside well production tubing by various devices attached to a wireline. Also, production flow control devices are installed in and removed from the tubing when necessary, by special tools attached to the end of a wireline.
Although wireline tool operations are still in widespread use, the use of coiled, or reeled tubing is becoming more popular since it enjoys advantages over wireline in certain operations. For example, coiled tubing can be used in connection with highly deviated or horizontal well completions since the coiled tubing does not rely on gravity for setting and retrieval of downhole devices. Coiled tubing has also proven to be advantageous from a time and money saving standpoint in connection with sand washing, fluid displacement, removal of paraffin, squeeze cementing, spotting acid, light duty drilling of cement and the like, fishing operations, and flow line clean out. With the recent availability of large diameter coiled tubing, increasingly heavier duty well drilling, servicing and completion operations are possible.
Since wireline and coiled tubing operations both enjoy separate and distinct advantages, it often is desirable to utilize both wireline and coiled tubing to service the same wells. For example, in some applications coiled tubing is used initially for performing washing and/or drilling functions in the wellbore, after which wireline tools are inserted into the wellbore for performing pressure surveys or pulling various flow control devices. In this example, a coiled tubing rig would initially be assembled over the wellbore, and would include a coiled tubing injector extending over a stripper, or stuffing box which, in turn, is connected to a blow-out preventor, or the like. A goose neck, or tubing guide, is usually connected to the upper portion of the injector for guiding the coiled tubing into the injector which forces the coiled tubing through the stripper and the blow-out preventor into the pressurized wellbore. However, the wireline and coiled tubing tools usually have a diameter greater than that of the coiled tubing and often have to be inserted in a pressure containing lubricator which has an even greater diameter. Therefore, since the strippers associated with the coiled tubing rig are often not large enough to receive the tools, the coiled tubing rig has to be disassembled, and the components necessary to guide the wireline or coiled tubing tools and their lubricators into the wellbore have to be assembled over the wellbore. These latter components usually include blow-out preventors and a lubricator assembly consisting of one or more sections to accommodate the tools being used. It is apparent that the disassembly of the coiled tubing rig and the assembly of other equipment above a high pressure well is time consuming and gives rise to potential equipment handling accidents.
The terms "coiled tubing tools" and "wireline tools" apply to a broad range of devices that can be usefully attached to coiled tubing or wireline for various processes including, but not limited to, drilling, logging, inspection, cleaning, completion and other routine well servicing operations.